Flint



Jan. 5, 1965 F. v. HUNT 3,16

FLINT Filed June 5, 1962 INV EN TOR FREDERICK V. HUNT BYM WM ATTORNEYS United States Patent Oflfice 3,164,447 FLINT Frederick V. Hunt, Belmont, Mass. Filed June 5, 1962, Ser. No. 200,163 4 Claims. (Cl. 29-193) The present invention relates to lighter flints.

The art is replete with various configurations and formulations of flint and flint-like substances, hereinafter generically referred to by the term flint, for enabling effective ignition of combustible materials through the action of hot flint particles. Flints have been widely used, for example, in commercial cigarette, cigar, and pipe lighters in which hot flint particles, produced by the action of a striking wheel grinding against the flint, cause ignition of the combustible-fuel-saturated wick or gas mixture.

One of the difliculties with flints employed in such devices, however, is that, after the flint has become worn down from about one-third to about one-half of its length, the igniting operation, upon rotation of the striking wheel, tends to become erratic and intermittent. Among the reasons for this is the fact that the striking wheel, engaging the concave end surface of the rod-like cylindrical flint, carries loosened particles from one edge of the end surface across the concave end surface to the oppositely disposed edge thereof, from which edge region the particles are ejected into space toward the wick or gas outlet. Except for those particles that may be loosened immediately adjacent the edge of the flint closest to the wick or gas outlet, the remainder of the loosened particles of flint become cooled as they are carried by the striking wheel across the concave end surface of the flint. Such carried particles, on becoming cooled, become useless and unable to produce ignition. Thus most of the bearing surface of the flint that is engaged by the striking wheel is rendered useless for ignition purposes; while at the same time the accumulation of such useless detached particles of the flint serves to increase the bearing pressure of the so-neutralized portion of the end surface of the flint against the mating portion of the striking wheel, and thereby serves to dilute the effect of the retaining spring by allowing only a small part of the spring force to be exerted against the part of the flint which is effective in yielding the hot sparks that can produce ignition. A major part of the torque required to rotate the striking wheel is, therefore, wasted in detaching and transporting flint particles which are cooled and rendered functionally useless.

An object of the present invention, accordingly, is to provide a new and improved flint construction which will overcome the disadvantages above-discussed by increasing the effective area of the flint from which hotflint-particles can be detached and reducing the area from which the detached particles are made useless by cooling.

A further object is to reduce the operating torque required to rotate the flint striking wheel by reducing the bearing area of the part of the flint which is operationally useless.

Another further object is to provide a novel flint configuration of improved reliability and more general utility.

Other and further objects will be explained hereinafter and will be more particularly pointed out in the appended claims.

In summary, from perhaps one of its broadest aspects, the present invention relates to a rod-like lighter flint provided with a groove, preferably a plurality of grooves, formed in the peripheral surface of the flint and extending a along the length dimension thereof. Most effective operation has been achieved with substantially helical 3,164,447 Patented Jan. 5, 1965 grooves, preferably three in number, which are equally spaced along the periphery of the flint and extend along the length dimension of the flint. Preferred constructional details will hereinafter be discussed.

The invention will now be described in connection with the accompanying drawing, FIG. 1 of which is a perspective view illustrating prior-art types of flint construction in lighter mechanisms of the character described and demonstrating the problem underlying the present invention;

FIG. 2 is a top elevation of the construction of FIG. 1;

FIG. 3 is a perspective view of a flint constructed in I accordance with a preferred embodiment of the present invention for overcoming this problem; and

FIGS. 4 and 5 are end views of modified flint constructions.

Referring to FIGS. 1 and 2, a striking wheel 3 is shown rotatable, in the direction of the arrow, for grinding against the left-hand concave end surface B of a cylindrical flint 1 of prior-art construction, the flint 1 being urged against the striking wheel 3 by a spring 5 disposed between the right-hand end of the flint 1 and the bottom surface of a holder 7 that houses the flint 1. A gas outlet or fuel-saturated wick region 9 is disposed adjacent the terminal point or region D of the left-hand (FIG. 1) or lower (FIG. 2) edge of the concave end surface B of the flint 1.

The hot particles of flint rubbed oif at the region D and ejected toward the immediately adjacent region 9 cause ignition. As before explained, however, the particles rubbed off by the wheel 3 in the major portion of the concave end surface B of the flint 1 (namely, from the opposite point or region A and over the intermediate concave surface region C) become cooled as they are carried by the wheel 3 toward the point or region D, and they accumulate against the concave end surface B, acting to dilute the action of the spring 5, providing few, if any, free particles that can reach the ejection region D hot enough to serve any useful purpose in ignition of the gas or saturated wick at 9.

In the limiting case, a single thin planar strip of flint would be most eflicient, since the Wheel 3 would cause particles to strike from all points of the edge of the thin strip. Unfortunately, however, it is not commercially possible to hold or orient such a thin strip, which would be sensitive to position orientation within the holder 7.

In accordance with the present invention, it has been found that the provision of a groove in the peripheral surface of the substantially circular cross-section cylindrical flint 1, extending along the direction of the length dimension of the flint, however, will result in an area for the emission of hot flint particles that is far greater than that of the effective region D for the cylindrical flint, and, in addition, will eliminate at least part of the ineffective region A-C.

As more particularly illustrated in FIG. 3, the flint 1' is preferably provided with three substantially equally transversely spaced grooves 2, 2' and 2", extending in helical or spiral fashion along the length dimension thereof. This construction is a close approximation to an equi-angular three-pointed star, or symmetrical Y, which would theoretically provide substantially two-thirds the above-mentioned ideal efliciency of a single broadside planar strip. The surface area occupied by the grooves 2, 2' and 2" is substantially greater than the ungrooved peripheral surface area intermediate the grooves, and the wheel 3 will thus have a large, complete inwardly curved groove region E for generating and chipping off hot sparks for use in the ignition process, as distinguished from the limited region D of FIG. 1 and the useless surface regions A-C thereof; thus more efliciently utilizing the concave end surface of the flint for the generation of sparks, and providing minimal diluting action against the force of the spring 5.

As a practical example, the flint 1' may have an approximate diameter of about substantially one-tenth of an inch, and the three substantially equally spaced spiral grooves 2, 2' and 2" may each have a depth of about forty thousandths of an inch. A suitable helical pitch of the grooves 2, 2. and 2" is one in which the helix has a quarter of a turn in substantially two-tenths of an inch of length of the flint 1. With flints of this character, it has been found that there is substantially no intermittent operation of the type that one encounters when the flint of FIG. 1, for example, becomes from one-third to one-half consumed. Indeed, flints constructed in accordance with the embodiment of FIG. 3 have been found to be reliably usable, without a single miss of ignition, until the complete flint is substantially all worn away.

While the invention is most efiectively employed with the embodiment of FIG. 3, which may be constructed by milling the grooves as the cylindrical fiint 1 is turned about in a lathe, or preferably by extruding the same with the spiral or helical twist therein, some of the advantages of the invention may also be obtained, though not so effectively, with the modifications shown in FIGS. 4 and 5. In the embodiment of FIG. 4, only the pair of symmetrical oppositely disposed helical grooves 2 and 2 is provided occupying the major portion of the peripheral surface area. In the embodiment of FIG. 5, a single helical groove 2 is shown. The device of FIG. 5 will be position sensitive, however, so that unless it is inserted in the right direction, the grooved edge 2 will not be adjacent the region 9, and the benefit of the invention,

even in part, will not be obtained. The construction of 3 FIG. 4, on the other hand, is somewhat less position sensitive, though the structure of FIG. 3 is optimum for minimal position sensitiveness.

Further modifications will also occur to those skilled in the art and all such are considered to fall within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A rod-like flint for a lighter, said flint having at least one longitudinal groove of concave cross-section, the transverse periphery of said groove occupying a major portion of the transverse periphery of said flint at one side of an axial plane through said flint, whereby in engagement of an end of said flint with a rotating striking wheel, the effective area for the emission of hot flint particles is increased and the inelfective area is reduced.

2. The fiint of claim 1, there being a plurality of said longitudinal grooves of concave cross-section.

3. The flint of claim 1, there being three equally spaced longitudinal grooves of concave cross-section, the whole cross-section of said flint being a close approximation to an equiangular three-pointed star.

4. The flint of claim 3, in which the diameter of the flint is about one-tenth of an inch, the grooves are about fortyflthousandths of an inch deep and are helical with a pitch about one-quarter turn in about two-tenths of an inch along the length of the flint.

References Cited in the file of this patent UNITED STATES PATENTS Re. 24,022 McNeill June 14, 1955 1,024,713 Andrews et al Apr. 30, 1912 1,762,281 Steclrcr June 10, 1930 2,396,114 Neuerburg Mar. 5, 1946 FOREIGN PATENTS 310,823 Germany Feb. 5, 1919 

1. A ROD-LIKE FLINT FOR A LIGHTER, SAID FLINT HAVING AT LEAST ONE LONGITUDINAL GROOVE OF CONCAVE CROSS-SECTION THE TRANSVERSE PERIPHERY OF SAID GROOVE OCCUPYING A MAJOR PORTION OF THE TRANSVERSE PERIPHERY OF SAID FLINT AT ONE SIDE OF AN AXIAL PLANE THORUGH SAID FLINT, WHEREBY IN ENGAGEMENT OF AN END OF SAID FLINT WITH A ROTATAING STRIKING WHEEL, THE EFFECTIVE AREA FOR THE EMISSION OF HOT FLINT PARTICLES IS INCREASED AND THE INEFFECTIVE AREA IS REDUCED. 